The overall goal of this grant application is to evaluate potential exposure to toxic pollutants in the municipal water distribution system in Flint Michigan during the unforeseen water crisis created by changes in the source and treatment of drinking water. Exposure to lead (Pb) and disinfection-by-products (DBPs) present in water distribution systems continues to be a source of risk to vulnerable populations. A rapid increase in elevated blood lead levels in children has followed the changes in water treatment. Levels of DBPs that exceed US EPA maximum contaminant levels have also been observed. While much is known about regulated DBPs, less is known about unregulated nitrogenous DBPs (NDBPs). The U.S. EPA is currently considering regulating NDBPs due to their enhanced cancer risk level. High levels of DBPs are paired with exceptionally low levels of chlorine residual found throughout the water distribution system. The low levels of chlorine are likely due, in part, to radical corrosion that has occurred within the system and may allow for the growth of and potential exposure to opportunistic plumbing pathogens. Finally, due to repeated assurances from government officials denying problems associated with drinking water quality and safety, there is a severe lack of trust between residents and government officials. Improved communication of scientific and risk information is critically needed and this disaster presents an opportunity to more effectively utilize modern modes of communication (e.g. social media such as Facebook). Through this unique opportunity to observe changes in water treatment and distribution in Flint, this transdisciplinary team will document and characterize exposure to potential toxicants as well as enhanced scientific understanding of the processes responsible for degraded water quality. Accordingly, the project team will: Aim 1 - quantify the concentrations of residual chlorine, DBPs and Pb that have resulted from the change in water supply and evaluate the toxicity of these complex chemical mixtures; Aim 2 - define potential exposure to toxic chemicals through Flint's drinking water system using a combined analytical and modeling approach Aim 3 - communicate results to water utility operators, government officials (city, state, and federal), public health agencies and residents using principles of risk communication through a variety of channels including social media.